Variable inductor band changing for vhf-uhf tuner



VARIABLE INDUCTOR BAND CHANGING FOR VHF-UHF TUNER Filed Aug. 24. 1967YOICHI SAKAMOTO l0 Sheets-Sheet 1 Dec. 1, 1970 3 m 0 LP, Wa I WIT M 1.ill:ll w v| Tm wt" w 4 n gt T SW1 ..n k m m a L mm m J wVIIIHHHUHUIIIIIIIIIHHHIIIM q 2 5 25 m F0 .3. w m 1/ I. 5/ E! r. wlwl 3 6J 3% M ;W L 7 2 i. U 9.. w

INVENTOR yOIcHI Jmm/wm ATTORNEYS 1970 YOICHI SAKAMOTO 3,544,9031

VARIABLE INDUCTOR BAND CHANGING FOR VHF-UHF TUNER l0 Sheets-Sheet 2Filed Aug. 24, 1967 I NVENTOR yOI CHI JHAAIIDTO ATTORNEYS 1970 YOICHISAKAMOTO 3,

VARIABLE INDUCTOR 'BAND CHANGING FOR VHF-UHF TUNER Filed Aug. 24, 196710 Sheets-Sheet 5 /0 Y I EVE/EEAPPL/ED VOLTAGE w 2 MUQEBWQVG FIG 4INVENTOR YDICH/ JAKRNOTO 5; m5 [Cy L14. e %Ww ATTORNEYS 1970 YOICHISAKAMOTO 3,544,903

VARIABLE INDUCTOR BAND CHANGING FOR VHF-UHF TUNER Filed Aug. 24, 1967 10Sheets-Sheet 4.

FREULE AMPL/F/ER FREQUENCY-- INVENTOR yolcm mm/10m ATTORNEYS 1 YOICHISAKAMOTO 3,54

VARIABLE INDUCTOR BAND CHANGING FOR VHF-UHF TUNER Filed Aug. 24, 1967 10Sheets-Sheet 6 INVENTOR yolol-ll .m lfH/ID r0 ATTORNEY S I970 YOICHISAKAMOTO 3,54

VARIABLE INDUCTOR BAND CHANGING FOR VHF-UHF TUNER Filed Aug. 24, 196710' Sheets-Sheet 7 TUNER INVENTOR y fil JHKHHDTO OJ. m BY Maw 521EATTORNEYS 1970 YOICHI SAKAMOTO ,9 3

VARIABLE INDUCTOR BAND CHANGING FOR VHF'UHF TUNER i0 Sheets-Sheet 8Filed Aug. 24, 1967 INVENTOR 1970 YOICHI SAKAMOTO 3,544,903

VARIABLE INDUGTOR BAND CHA NGING FOR VHF-UHF TUNER Filed 1967 1oSheets-Sheet 1o "F/G. 20 H FIG 2/ 6 m q A Q h R \1 \m k 85 b 35% 1 m I'5 W Q 1% //VTERMED/ATE g ED/A7E FREQUE/VcY g Qg FREQ/ENC) Q 91 E 8 P76.22

A OFF OFF 4 OFF 19mm 1 I I z i i I: i //vTER/vE0/ATE mum 1mm mum 1mm!IHHH gfigg f l E OUTPUTOF 6 W WWW E 2 i OUTPUT 0 1 1 SWEEP C/RCU/T I 1 ID 2 INVENTOR 'ymcm Jmmnmo ATTORNEYS United States Patent 3,544,903VARIABLE INDUCTOR BAND CHANGING FOR V TUNER Yoishi Sakamoto,Toyonaka-shi, Japan, assignor to Matsushita Electric Industrial Co.,Ltd., Osaka, Japan, a corporation of Japan Filed Aug. 24, 1967, Ser. No.662,916 Claims priority, application Japan, Aug. 30, 1966, 41/57,750;Sept. 2, 1966, 41/58,426; Dec. 28, 1966, 42/247; Jan. 19, 1967,42/4,284; Jan. 26, 1967, 42/5,527; Jan. 27, 1967, 42/11,507; Mar. 1,1967, 42/115,530; Apr. 14, 1967, 42/24,128

Int. Cl. H03j 5/02 US. Cl. 325-459 5 Claims ABSTRACT OF THE DISCLOSURE Atuner using variable capacitance diodes as elements for changing thetuning and oscillation and which is adapted to effect the desiredselection of television broadcast by applying different voltages to thevariable capacitance diodes.

This invention relates to a tuner for television use.

The television tuners presently available are so designed as to effectchannel selection by switching channel selecting coils corresponding tothe frequencies assigned to respective broadcasting stations by means ofa turret switch or disk turret switch. In this case, it goes withoutsaying that the number of the band selecting coils to be provided in atelevision receiver should be at least equal to that of the broadcastingstations. Besides, it is also required that such coils be incorporatedin the tuning circuit, local oscillator circuit, etc. of such receiver.Therefore, the number of contacts needed to switch these coils becomesas large as 50 to 100. Inevitably, this limits the life of such contactportions in spite of a careful design and fabrication of the latter. Atpresent, a majority of trouble of a television receiver is that of thetuner due to malfunction of such contacts.

In view of this, an attempt has been made to improve the performance ofsuch tuner through the use of contacts formed of a precious metal whichis relatively free from abrasion. However, it would be impossible tocompletely eliminate the trouble of a tuner without resorting to meansfor basically solving the contact problem.

In the tuner circuit according to the present invention, variablecapacitance diodes of which the capacitance is varied by changing avoltage applied thereto are used as tuning and oscillation variableelements of such circuit.

Thus, the most important object of this invention is to provide anarrangement capable of receiving any desired television broadcast bychanging a voltage applied to the variable capacitance diodes.

The ratio of the minimum frequency to the maximum frequency used intelevision broadcast is 90:222 in the Japanese system and 542216 in theUnited States system. Therefore, if it is desired to receive theover-all television broadcast frequency hand through variations incapacitance of variable capacitance diodes alone, then the ratio of themiminum capacitance to the maximum capacitance of such a diode becomes1/90 :1/222 1:1/6.1 in

3,544,903 Patented Dec. 1, 1970 ice the Japanese system and 1/54 :1/2161:1/16 in the US. system, since the resonance frequency is defined byzwfd (1 and the following relation is derived therefrom Japanese system:

Channels 1 to 3, mc. to 108 mc.; Lower band Channels 4 to 12, me. to 222mc.; Higher band American system:

Channels 2 to 6, 54 mc. to 88 mc.; Lower band Channels 7 to 13, 174 mc.to 216 mc.; Higher band Then, the ratios of the maximum to the minimumcapacitance of a variable capacitance diode become as follows:

Japanese system:

Lower band; 1/90 :1/108 1:1/1.44 Higher band; 1/170 :1/222 1:1/1.7American system:

Lower band; 1/54 :1/88 l:/2.65 Higher band; 1/174 :1/126 1:1/1.54

These values may be readily be attained.

In accordance with an object of this invention, therefore, variablecapacitance diodes are used as tuning and oscillation variable elementsof the tuner circuit, and the lower band of the entire televisionbroadcast frequency band, for example, is received by changing a voltageapplied to the variable capacitance diodes and when a channel within thehigher band is to be selected, the inductances of coils constituting thetuning and oscillator circuits of the tuner circuit together with saidvariable capacitance diodes are electrically changed to select anydesired channel within the higher band, thereby making it possible toselectively receive all the television broadcast.

Other objects, features and advantages of this invention will becomeapparent from the following description taken in conjunction with theaccompanying drawings.

FIG. 1 is a circuit diagram illustrating the tuner circuit according toan embodiment of this invention;

FIG. 2 is a circuit diagram showing the tuner circuit according to asecond embodiment of this invention;

FIG. 3 is a circuit diagram showing the tuner circuit according to athird embodiment of this invention;

FIG. 4 is a view illustrating the voltage-current characteristic of avariable capacitance diode;

FIG. 5 is a circuit diagram showing the tuner circuit according to afourth embodiment of this invention;

FIG. 6 is a view illustrating the relations between reverse appliedvoltage and capacitance of a variable capacitance diode;

FIG. 9 is a view illustrating the discriminating action;

FIG. 10 is a circuit diagram showing the tuner circuit according to afurther embodiment of this invention;

FIG. 11 is a circuit diagram showing a further embodiment wherein thetuner circuit is divided into a higher band tuner and a lower bandtuner;

FIGS. 12a and 12b are frequency characteristic diagrams for explainingthe operation of the tuner circuit of FIG. 10;

FIG. 13 is a view showing the frequency vs. reactance characteristic ofthe circuit 704 shown in FIG. 11;

FIG. 14 is a view showing the frequency vs. reactance characteristic ofthe circuit 704" shown in FIG. 11;

FIG. 15 is a circuit diagram illustrating still another embodiment ofthis invention;

FIG. 16 is a schematic circuit diagram showing an example of highfrequency tuning circuit incorporated in the conventional selectingcircuit;

FIGS. 17 and 18 show the high frequency tuning circuits according tothis invention;

FIG. 19 shows a still further embodiment of this invention;

FIG. 20 shows the intermediate frequency vs. output voltagecharacteristic of the frequency discriminator circuit incorporated inthe arrangement of FIG. 19;

FIG. 21 illustrates the characteristic of the intermediate frequencyamplifier provided in the arrangement of FIG. 19; and

FIG. 22 is a view illustrating the operation of the circuit as shown inFIG. 19.

Referring to FIG. 1 of the drawings, the reference numeral 12 representsan input terminal, and 13 a tuning coil wound on a magnetic core whichis magnetized by a D.C. current. The coil 13 constitutes, together witha variable capacitance diode 14, a single-resonance circuit of which theoutput is applied to an amplifier transistor 16 through a capacitor 15.Between the collector and the emitter of the amplifier transistor 16 isprovided a doubletuning circuit consisting of coils 17 and 18 similar tothe coil 13 and variable capacitance diodes 19 and 20. The output of thedouble-tuning circuit is applied to a mixer transistor 21 to which issimultaneously supplied the output of a local oscillator circuit 22.Thus, a video intermediate frequency signal is obtained at the collectorof the transistor 21.

The reference numeral 23 denotes a variable power source which isconnected with a variable capacitance diode 28 of the local oscillatorcircuit 22 and said variable capacitance diodes 20, 19 and 14 throughresistors 24, 25, 26 and 27, respectively.

A power source 30 is connected with the respective coils 13, 17 and 18and a similar coil 29 of the local oscillator circuit through a switch31 by which the power source is turned on and off.

Capacitors 32, 33, 34, 35, 36, 37 and 38 and coils 39, 40, 41 and 42serve to electrically isolate the respective coils 13, 17, 18 and 29from each other.

Description will now be made of the operation of the circuit asillustrated in FIG. 1. When the switch 31 is opened, no power issupplied to the respective coils 13, 17, 18 and 29, so that each ofthese coils will have a high impedance because of its high permeabilitywith a result that the circuit becomes ready for operation in the lowerband. In such a state, if a signal arrives at the input terminal, itwill be single-tuned by means of the coil 13 and the variablecapacitance diode 14, and then the resultant tuned frequency signal willbe amplified by the transistor 16 of which the output will in turn bedoubletuned by means of the double-tuning circuit so as to be suppliedto the mixer transistor 21. At the sametime, the output of the localoscillator circuit will be supplied to the base of said mixer transistor21. Thus, a video intermediate frequency signal will be obtained at thecollector of the transistor 21.

By changing the voltage of the power source 23 to change the capacitanceof each variable capacitance diode 14, 19, 20 and 28, the tunedfrequencies of the singletuning circuit and double-tuning circuit andthe frequency of oscillation of the local oscillator circuit 22 arecorrespondingly changed, so that the selection within the lower bandbecomes possible.

Closing the switch 31 for the power source 30 causes an energizingcurrent to flow through each of the coils 13, 17, 18 and 29 so thatthese coils are magnetized in accordance with the fiat portion of the BHcurve, with a result that the values of ,u. of these coils and, hence,their impedances are decreased. This results in the selection of thehigher band. By changing the voltage of the power source 23 to changethe capacitances of the variable capacitance diodes, it is possible toachieve the selection within the higher band.

As described above, the switching operation for the higher and lowerbands is current-wise effected by virtue of the non-linearity ofmagnetization of a magnetic material provided in the tuning andoscillation coils, and the selection within each band is voltage-wiseefiected by means of the variable capacitance diodes for the purpose ofelectrically selecting a desired channel. Thus, the band switchingoperation between the higher and lower bands can be performed byapplying or interrupting a D.C. magnetic field to a core formed of amagnetic material with a remarkable non-linearity of magnetization tochange the permeability ,u. of the core and thereby change theinductance of the coil.

In FIG. 2 there is illustrated another embodiment of this inventionwherein the band switching operation between the higher and lower bandsis effected through displacement of a magnetic material such as highfrequency ferrite or the like. The tuner circuit comprises a tuningcircuit 101, a double-tuning circuit 102 and a local oscillator circuit121. The circuit 101 includes a series connectron of two coils 107 and108 and a variable capacitance diode 103 connected thereacross. Thecircuit 102 contains a series connection of two coils 109 and 110 and avariable capacitance diode 104 connected thereacross, and a seriesconnection of coils 111 and 112 and a variable capacitance diode 105connected thereacross. The circuit 103 comprises a series connection ofcoils 113 and 114 and a variable capacitance diode 106 connectedthereacross. Magnetic members 115 are associated with the COllS 108,110, 112 and 114 through a cam or plunger mechanism, respectively. Ifthe magnetic members 115 are inserted into or placed close to the coils108, 110, 112 and 114, the inductance of each coil is increased to avalue suitable for selection of the lower band, while if the magneticmembers 115 are retracted or spaced apart from the coils 108, 110, 112and 114, the inductance of each coil is decreased to a value suitablefor selection of the higher band. Thus, the band switching operationbetween the higher and lower bands can readily be performed. By applyinga voltage different from a power source to the variable capacitancediodes 103, 104, 105 and 106 through resistors 116, 117, 118 and 119,respectively, it is possible to achieve the selection within each band.

FIG. 3 shows the case where coils forming the tuning circuit andoscillator circuit of the tuner circuit together with variablecapacitance diodes are divided into two portions, a diode is coupled tothe intermediate point between the two divided portions of each coil,and one of the divided portions of each coil is connected anddisconnected through the associated diode, thereby effecting the bandswitching operation between the higher and lower band. Detailedexplanation will now be made with reference to FIG. 3, wherein thereference numeral 201 represents a high frequency tuned amplifiercircuit, 202 a double-tuning circuit, 203 a local oscillator circuit and204 a mixer circuit. The output of the high frequency tuned amplifiercircuit 201 is applied to the double-tuning circuit 202 the output ofwhich is in turn mixed with the output of the local oscillator circuitin the mixer circuit 204 so that an intermediate frequency signal isproduced.

The reference numerals 205, 206 and 207 represent transistorsconstituting the high frequency tuned amplifier circuit 201, mixercircuit 204 and local oscillator circuit 203, respectively. Thereference numerals 208, 209, 210 and 211 denote variable capacitancediodes connected in the respective circuits 201, 202 and 203 and thevariable capacitance diodes 208, 209, 210 and 211 constitute tuningcircuits or LC oscillator circuits together with inductors 213 and 214,215 and 216, 217 and 218 and 219 and 220.

Thus, by changing the value of a power source 12 applied to the variablecapacitance diodes 208, 209 210 and 211, the capacitance of each ofthese diodes is changed, so that the receiving condition of each circuitis varied.

Diodes 221, 222, 223 and 224 have their cathodes grounded and theiranodes connected with power source 226 or 227 through the connectionpoints of the inductors 213 and 214, 215 and 216, 217 and 218 and 219and 220 of the circuits 201, 202 and 203 and a switch 225 respectively.Normally, it is possible to construct a circuit which is adapted forconduction or non-conduction by applying a positive or negative voltageacross the terminals of a diode. Assume that a channel in the higherband is desired to be received. By bringing the movable contact of theswitch 225 into engagement with the contact a, a DC. current is causedto flow through each of the diodes 221, 222, 223 and 224. Thus, suitableselection of the values of resistors 227, 228, 229 and 230 causes thevalue of dV/dl to be close to zero at the operating point of each of thediodes 221, 222, 223, 224 as illustrated in FIG. 4, with the result thatthese diodes become conductive so as to cause the ends of coils 213,215, 217 and 219 to be grounded. From this, it will be noted that in anattempt to receive a channel within the higher band, the inductors 213,215, 217 and 219 are used while the other inductors 214, 216, 218 and220 are shorted so that the latter inductors appear as if they wereabsent. In this way, any channel within the higher bands can be selectedby changing the voltage of a variable voltage source 212 while theswitch 225 is being engaged with the contact a.

In order to receive a channel within the lower band, the switch 225 isswitched to the contact b so that a negative voltage is applied to thecathodes of the diodes 221, 222, 223 and 224. This substantiallyprevents a current flow through the diodes 221, 222, 223 and 224 andthus a voltage substantially equal to that of the power source 227 isapplied to these diodes so that the diodes become non-conductive butthey have a slight barrier capacitance, which is substantiallynegligible. Hence, the tuning in ductances of the high frequencyamplifier circuit 201, tuning circuit portion 309, interstate tuningcircuit porresented by the sum of the inductance of the inductors 213and 214, that of 215 and 216, that of 217 and 218 and that of 219 and220, respectively. In such a state, any channel within the lower bandcan be selected by changing the voltage of the variable voltage source212.

FIG. illustrates a further embodiment of this invention which is adaptedfor switching the higher and lower bands. Description will now be madeof the embodiment shown in this figure, wherein the reference numerals301, 302, and 303 denote a high frequency amplifier transistor, mixertransistor and a local oscillator transistor, respectively, and thereference numerals 304, 305, 306 and 307 represent channel selectingvariable capacitance diodes provided in an input tuning circuit portion308, inter-stage tuning circuit portion 309, interstate tuning circuitportion 310 and local oscillator circuit, respectively. The inductanceelement portion of said input tuning circuit 308 is composed of a seriesconnection of coils 308a and 308b. Similarly, the inductance elementportion of the interstage tuning circuit portion 309 is formed by aseries connection of coils 309a and 30% that of the inter-stage tuningcircuit portion 310 by a series connection of coils 310a and 310b, andthat of the local oscillator circuit portion 311 by a series connectionof coils 311a and 311b. The reference numerals 312, 313, 314 and 315represent band switching variable capacitance diodes connected inparallel with said coils 3081), 309b, 3101; and 311b, respectively. Avoltage E of a DC. voltage source 317 and a voltage E of a DC. voltagesource 318 superimposed upon the voltage E are selectively applied tothe diodes 312, 313, 314 and 315 as reverse voltage through a bandchange-over switch 316.

The reference numeral 319 denotes a variable DC voltage source to applya desired reverse voltage to said channel selecting variable capacitancediodes to achieve channel selection.

The characters X, Y and Z in FIG. 6 show three different types ofdependence of barrier capacitance upon applied voltage of a variablecapacitance diode as a reverse voltage is applied thereto. The variablecapacitance diodes utilized in this invention may take any one of thesethree types of characteristic.

Description will now be made of the channel selecting operation. Assumethat a channel within the lower band is to be received. Then, the switch316 is switched to the contact a, so that a high reverse voltage of(EH-E is applied to the variable capacitance diodes 312, 313, 314 and315, with the result that their barrier capacitances are greatlydecreased. If the value of (E +E is previously adjusted so that each ofsuch barrier capacitances represents a minimum value, the parallelimpedance circuits formed by the variable capacitance diode 312 and coil308b variable capacitance diode 313 and coil 30% variable capacitancediode 314 and coil 310b, and variable capacitance diode 315 and coil311b are regarded as being inductive. Since these parallel impedancecircuits are connected in series with the coils 308a, 309a, 310a and311a (it is assumed that their inductance values are L L L and Lrespectively), the tuning inductance values of the input tuning circuitportion 308, inter-stage tuning cir cuit portion 309, inter-stage tuningcircuit portion 310 and local oscillator circuit portion 311 becomeapproximately L +L L -i-L L +L and L +L respectively, where L L L and Lare the inductance values of the coils 308b, 3091), 31011 and 311b.Thus, the tuning inductances assume values suitable for the operationwithin the lower band. In such a state, therefore, desired channelselection can be achieved by changing the voltage of the DC. volt agesource 319 to change the reverse voltage applied to the variablecapacitance diodes 304, 305, 306 and 307, so that any desired channelwithin the lower band can be received.

In an attempt to receive a channel within the higher band, the switch316 is switched to the contact b, so that only a low reverse voltage Efrom the DC. voltage source 317 is applied to the variable capacitancediodes 312, 313, 314 and 315. As a result, the barrier capacitances ofthese diodes are greatly increased. In this case, if the voltage E isadjusted so that each of such barrier capacitances represent amaximurnvalue, the parallel impedance circuits formed respectively by thevariable capacitance diode 312 and coil 308b, variable capacitance diode313 and coil 30%, variable capacitance diode 314 and coil 31011, andvariable capacitance diode 315 and coil 311b become capacitive, and thetuning inductances in the input tuning circuit portion 308, inter-stagetuning circuit portion 309', inter-stage tuning circuit portion 310 andlocal oscillator circuit portion 311 become substantially equal to theinductances L L L and L, of the coils 308a, 309a, 310a and 311a,respectively. Thus the tuning inductances assume values suitable for theoperation within the higher band.

In such a state, therefore, channel selection can be achieved bychanging the voltage of DC. voltage source 319 so as to change thereverse voltage applied to the variable capacitance diodes 304, 305, 306and 307, so that any desired channel within the higher band can bereceived.

Although, in the embodiment of FIG. 5, the mechanical switch 316 wasused as means for switching the reverse voltage applied to the variablecapacitance diodes 312, 313, 314 and 315, use may equally be made of anelectronic switch such as gate circuit. Furthermore, the DC. voltageapplied to the variable capacitance diodes 304, 305, 306 and 307 may bea voltage divided by means of a potentiometer or a sweep voltage such assaw-tooth voltage. Obviously, the inter-stages may be single-tuningcircuits rather than double-tuning circuits, and the active elementsmaybe vacuum tubes rather than transistors.

In the foregoing, description has been made of the embodiments adaptedfor switching the higher and lower bands. In this case, a variation inthe control voltage applied to the variable capacitance diodesinevitably leads to a drift in the frequency of local oscillation.Furthermore, variations in the capacitance of such diodes withtemperature cannot be neglected. This makes it impossible to achieveperfect selection of a desired channel. In order to achieve such perfectselection, therefore, the control voltage applied to the variablecapacitance diodes should be automatically controlled to an optimumvalue.

FIG. 7 shows a circuit diagram of a channel selecting device usingvariable capacitance diodes as tuning changing elements. In this figure,the reference numeral 401 indicates a high frequency amplifier circuit,402 a doubletuning circuit, 403 a mixer circuit, and 404 a localoscillator circuit.

The reference numerals 405, 406 and 407 represent a high frequencyamplifier transistor, a mixer transistor and a local oscillatortransistor, respectively, and the reference numerals 408, 409, 410 and4.11 denote variable capacitance diodes serving as channel selectionchanging elements included in the respective circuits above,respectively.

The reference numeral 412 represents a power source for applying avoltage to the variable capacitance diodes 408, 409, 410 and 411.

The reference numeral 413 denotes a constant voltage diode, 414 atemperature-dependent resistor for compensating for the temperaturecharacteristics of the variable capacitance diodes, and 415 a controlvoltage circuit for applying a different voltage to the respectivevariable capacitance diodes 408, 409, 410 and 411 depending upon thechannel to be selected. By turning on and off switches S to S thevoltage applied to the variable capacitance diodes 408, 409, 410 and 411is varied to change the capacitances of these diodes so that any desiredchannel can be selected.

Thus, any variations in voltage of the power source 412 and incapacitance of the variable capacitance diodes with temperature can becompensated by means of the constant voltage diode 413 andtemperature-dependent resistor 414, so that a fairly suitable voltagecan be applied to the variable capacitance diodes 408, 409, 410 and 411.However, perfect correction cannot be effected due to aging of eachcomponent, influence of temperature characteristics, changes intemperature characteristics of capacitance of the variable capacitancediodes depending upon applied voltage, and the like. Thus, an accuratevoltage can hardly be applied to the variable capacitance diodes, whichmakes it difficult to achieve accurate selection of a desired channel.

FIG. 8 shows an arrangement adapted for eliminating the afore-mentioneddrawbacks. First, description will be made of the point where thearrangement of FIG. 8 differs from that of FIG. 7. The circuit of FIG. 8is characterized in that a frequency discriminator 517 is insertedbetween the output terminal 518 of an intermediate frequency amplifier516 connected with the output terminal of a mixer circuit 503 and theconnection point between a variable capacitance diode 511 and a resistor519 connected in series with each other.

Thus, an intermediate frequency signal taken out of the mixer circuit503 is amplified in the intermediate frequency amplifier 516 and part ofthe output of the amplifier is supplied to the frequency discriminator517.

A control voltage represented by a curve a of FIG. 9 is applied insuitable polarity from the frequency discriminator 517 to the connectionpoint between the variable capacitance diode 511 and the resistor 519.

On the other hand, the frequency of oscillation of the local oscillatorcircuit is controlled in accordance with such a characteristic asrepresented by a curve 11 of FIG. 9. Thus, the automatic control loopbecomes stable at the intersection between the curves a and b or at thefrequency indicated by A, so that normal video and sound broadcast canbe received.

Further description will now be made of the operation of the circuit asshown in FIG. 8. If it is desired to receive a certain channel, one ofthe switches S to S of the voltage control circuit (potentiometer) 515is turned on so that a control voltage most suitable for the receptionof said certain channel is applied to the respective variablecapacitance diodes 508, 509, 510 and 511 thus achieving the selection ofthe desired channel.

Even if the voltage of the power source 512 is changed, suitablereception can equally be achieved.

That is, if the voltage of the power source is decreased, the voltageapplied to the respective variable capacitance diodes is correspondinglydecreased, so that the capacitance of, for example, the variablecapacitance diode 511 is increased to cause the frequency of oscillationto be decreased.

Such decrease in the frequency of the local oscillation leads todecrease in the intermediate frequency so that the output frequency ofthe intermediate frequency amplifier 516 is likewise decreased, with theresult that an input frequency fed back to the frequency discriminator517 is also decreased.

Consequently, the output voltage of the discriminator 517 is decreased,as illustrated in FIG. 9.. With such decrease in the output of thefrequency discriminator 517, the voltage applied to the variablecapacitance diode 511 is increased.

The increase in the applied voltage leads to decrease in the capacitanceof the variable capacitance diode 511, thus increasing the frequency oflocal oscillation to a predetermined constant value.

In this way, variations in the voltage of the power source can becompensated.

FIG. 10 shows an arrangement in which no frequency discriminator circuitdescribed above is provided and a control voltage for fine adjustment isapplied directly from a part of an audio intermediate frequencyamplifier 618 to the variable capacitance diode of the local oscillatorcircuit. The video IF amplifier circuit 616 is so designed as to have afrequency response shown in FIG. 12a, where the abscissa and theordinate represent frequency and reciprocal of the amplification degree.A portion of the video IF amplifier circuit 616 is then fed to thejunction 620 between the variable capacitance diode 611 via the audio IFamplifier circuit 618. The diode 611 constitutes the resonant element ofthe local oscillator circuit 604. Due to the frequency characteristicsof the video IF amplifier circuit 616 as shown in FIG. 12a, the inputcontrol voltage to the junction 620 is such as is shown by a curve a inFIG. 1211. Meanwhile, characteristic line b of FIG. 12b represents theoutput of the local oscillator circuit 604 with respect to theoscillation frequency of the circuit, so that at the intersection pointA between the curve a and line b the operation of the local oscillatorcircuit 604 is stabilized. Thus, a similar effect can be producedwithout providing any frequency discriminator circuit described above.

In FIG. 11, there is shown an arrangement in which the tuner circuit isdivided into two sections, or a higher band tuner and a lower bandtuner.

In the case where the tuner is divided into a higher band one and alower band one as described above, the mixer circuit can be used incommon with respect to both of the higher and lower band tuners.However, such common use of the mixer circuit causes the higher andlower band tuners to have an electrically adverse effect upon each othersince they are electrically connected with each other through a certainmeans.

Hence, when a channel within the higher band is selected by means of thehigher band tuner, for example, the lower band tuner will disturb thenormal function of the higher band tuner. This problem can effectivelybe solved by the arrangement of FIG. 11, wherein the reference numeral701 represents a higher band tuner, 702 a lower band tuner, and 703 aninput terminal associated with both of the higher and lower band tuners.

Description will now be made of the composition of the higher band tuner701 which comprises a high frequency input circuit 704, a high frequencytuned amplifier circuit 705, a local oscillator circuit 706 and a mixercircuit 707. A radio wave received at the input circuit 704 is tuned andamplified in the high frequency tuned amplifier circuit 705 so that apredetermined television signal is produced which is in turn mixed witha signal produced by the local oscillator circuit 706. Thus, anintermediate frequency is obtained at a terminal 708.

On the other hand, the lower band tuner 702 is so designed that a signalentering a high frequency input circuit 709 is amplified in a highfrequency tuned amplifier circuit 710 and then supplied to a mixercircuit 707 together with the output of a local oscillator circuit 711.Thus, an intermediate frequency is obtained at the terminal 7 08.

A power source is always supplied to the mixer circuit 707 through aterminal 712, and it is selectively supplied to the higher band tuner701 and the lower band tuner 702 by switching a change-over switch 713to a terminal L or H.

When a certain channel within the higher band is to be received with thepower source switched to the terminal H, if a channel signal in thelower band is mingled with the signal in the higher band tuner, thesignal is transmitted from a tuning circuit 714 of the high frequencytuned amplifier circuit 705 of the higher band tuner 701 to a tuningcircuit 715 of the high frequency tuned amplifier 710 of the lower bandtuner 702 which is rendered inoperative, so that it is also tuned in thetuning circuit 715 since the tuning circuit 714 is coupled to the tuningcircuit 715 on the input side of the mixer circuit 707. Thus, anundesirable phenomenon as interference occurs in the mixer circuit 707.In order to prevent such phenomenon, a higher band pass filter circuit 704' which is adapted to greatly attenuate the lower band signal isprovided in the input circuit of the higher baud tuner 701. Thefrequency vs. reactance characteristic of the circuit 704' is as shownin FIG. 13, and this circuit is designed so that the frequency foocorresponding to the pole point is selected to be in the neighborhood ofthe center of the lower band and the frequency f corresponding to thezero point is selected to be in the neighborhood of the center of thehigher band. Thus, the filter circuit 704' functions as a two-terminalcircuit which represents a low impedance with respect to the higher bandand a high impedance with respect to the lower band.

In this way, any signal within the lower band is cut off so that anydesired signal within the higher band can be obtained, thus preventinginterference due to the fact that the lower band tuner operates duringthe selection of a channel within the higher band. In addition, sincethe circuit arrangement described above represents a high impedance withrespect to the lower band, substantially no loss is caused on the inputside of the high frequency 10 amplifier circuit 710 of the lower bandtuner when a desired channel within the lower band is to be received, sothat deterioration in the gain and negative feedback performance can -beprevented.

A circuit 704" inserted in the input circuit 709 of the lower band tuner702 has such a frequency vs. reactance characteristic as shown in FIG.14, wherein the frequency foo corresponding to the pole point isselected to be in the vicinity of the center of the higher band and thefrequency corresponding to the zero point is selected in theneighborhood of the center of the lower band. The function of thecircuit 704 is quite similar to that of the circuit 704, except that thehigher band is changed to the lower band.

By switching the switch 713 to the terminal H to render the higher bandtuner 701 operative, as shown in the drawing, the power source issupplied to the high frequency tuned amplifier circuit 705 and the localoscillator circuit 706. In this case, the mixer circuit 707 is alwaysfed with the power source from the power source terminal 712. Thus, anychannel within the higher band (4 to 12 channels in the Japanese system)can be selected by applying a variable voltage from a terminal 722 tovariable capacitance diodes 716, 717 and 718.

Similarly, any channel within the lower band (1 to 3 channels) can beselected by switching the change-over switch 713 to the terminal L.

As described above, the mixer circuit can be used in common, and thecauses for interference between the higher and lower band tuners can beeliminated, resulting in a reduced loss of the inputs to the higher andlower band tuners. In this way, it is possible to develop a tuner of animproved performance.

FIG. 15 shows the case where the channel selecting operation of atelevision receiver of this type is effected on a remote control basisat a position remote from the receiver. An example will be describedwith reference to FIG. 15, wherein the reference numeral 801 representsa tuner portion of the television receiver, and 'D D and D are channelselecting variable capacitance diodes incorporated in the input circuit,inter-stage circuit and local oscillator circuit included in the tuner801, respectively, these diodes being shown as being taken out of thetuner portion for the illustrative purpose. E is a power source forselecting a desired channel, and E and E, are power sources which areapplied to the tuner 801 to effect the channel switching operationbetween the higher and lower bands. Although in this figure, E and E areshown as being of opposite polarities, they may be of a single polaritywhen the tuner is such as is shown in FIG. 5.

The reference numeral 802 denotes a connector adapted to connect therespective lead wires from a controller 803 to the television set, and Pto P are connection terminals provided in the connector #802. All theabove elements are incorporated in the television set.

The controller 803 consists of a variable resistor 804 divided into twosections and a switch 805. The both terminals of the power source E areconnected with fixed contacts 806 and 807 of the variable resistor 804through the contacts P and P of the connector 802 and suitable resistors808 and 809 respectively, and a slide contact 810 of the variableresistor 804 is connected with the variable capacitance diodes D D and Dthrough of the variable resistor 804 over the fixed contacts 806 fromthe left to the right (as viewed in the drawing), so that the barriercapacitances of these diodes are decreased. Thus, the channel receivedby the tuner is gradually changed from a lower one to a higher one.

Such change-over is required because the television broadcast band isdivided into two segments or more, for example, a higher one and a lowerone (1 to 3 channels and 4 to 12. channels).

To meet such requirement, there is provided the switch 805. The switch805 is actuated in interlocking relationship with the slide contact 810and designed so that it assures the position b when the slide contact810 slides on the fixed contacts 806 while it assumes the position awhen the slide contact 810 slides on the fixed contacts 807.

When the switch is placed in engagement with the contact a, a positivevoltage is applied from the power source E to the tuner through thecontacts P and P so that the tuner is made ready to receive any channelin the higher band by driving switching elements such as diodes, whilewhen the switch is brought into engagement with the contact b, anegative voltage is applied from the power source E to the tuner 801through the contacts P and P so that the tuner is made ready to receiveany channel in the lower band.

In the foregoing, the polarities of the power sources E and E have beenfixed for the sake of explanation, but this is not by way of limitation.It is to be noted that it is only required that, any power sources toensure the desired band switching operation of the tuner be connectedwith the latter.

Furthermore, the band switching circuit provided in the tuner may takeany form.

Alternatively, the switch 805 may be mounted on a shaft common to thatof the variable resistor 804 so that the switch may be operated throughforward or backward movement of the shaft. In this case the switch 805may be provided with increased terminals and another power source may beprovided in addition to the power sources E and E to control a UHFtuner. Thus, it may be possible to achieve remote control with respectto the entire VHF-UHF channels.

In the foregoing, description has been made of tuners using a channelselecting arrangement wherein the television broadcast frequency band isdivided into the higher band and the lower hand because of thelimitation of the capacitance variation range of variable capacitancediodes used as tuning and oscillation changing elements. However, suchband division increases the manufacturing cost. Therefore, it is desiredthat the channel selection be achieved without dividing the televisionbroadcast band into the higher band and the lower band. However, it isimpossible to further expand the capacitance variation range of thepresently available variable capacitance diodes due to theircharacteristics. Now, description will be made of an arrangement whereinuse is made of variable capacitance diodes of which the characteristicis left as it is but the television broadcast band is not divided intothe higher band and the lower band. In the conventional channelselecting device of this type, its high frequency tuning circuit isconstructed as shown in FIG. 16. That is, a variable capacitance diode902 is connected in parallel with an inductance 901 to form a parallelresonance circuit which is adapted to perform tuning operation.

With such arrangement, the capacitance variation range C -C of thevariable capacitance diode 912 is given by where C is the distributedcapacitance of the circuit, and f and f represent the upper and lowerlimits of the required tuning frequency range, respectively.

As will be seen from the Equation 1, the distributed capacitance Cserves to decrease the value of f /f and in order to maintain f /f at aconstant value, it is required that the capacitance variation range C Cbe increased.

Therefore, the arrangement of FIG. 16 requires a very wide capacitancevariation range of the variable capacitance diode 902. However, it isimpossible to ensure the tuning operation with respect to televisionwaves of a wide frequency range by means of a single variablecapacitance diode, which will be understood from the characteristics ofthe commercially available variable capacitance diodes.

For this reason, a tuning arrangement wherein the television band isdivided into the higher band and the lower band has been used, asdescribed above.

In accordance with this invention, there is provided an arrangementwherein the capacitance variation ratio of a variable capacitance diodeis effectively utilized without any further improvements in thecharacteristic relating to the capacitance variation range of thevariable capacitance diode and the tuning operation is performed withoutdividing the television band into the higher band and the lower band.

An example of this arrangement according to the present invention willnow be described with reference to FIGS. 17 and 18. As shown in FIG. 17,a series resonance circuit is formed by a capacitor 904, a tuning coil905, and a variable capacitance diode 906, and this circuit functions asa tuning circuit so that a tuned signal is taken out from a coil 907representing a suitable impedance.

In this case, the variable capacitance diode 906 can directly beconnected with the tuning coil 905 and a dis tributed capacitance Cwhich is in parallel with the diode 906 is negligible as compared withthe capacitance ratio of the diode 906 since the distributed capacitanceis separated by the inductance of the tuning coil 905.

Assume that the capacitance of the condenser 904 is C then the compositecapacitance C of the condenser 904 and the distributed capacitance C isgiven by the following Equation 2.

Hence, a tuned frequency f is given by CC c'+ c (3 where C is thecapacitance of the variable capacitance diode 6. The upper and lowerlimits f and f of the tuned frequency are as follows:

1 f fi 1 fmin min c'+o.... From Equations 4 and 5 is derived thefollowing relation:

1 1 max 2 arin i Normally, it is possible that C is several pf. orlarger, C to 20 pf. and C several pf. or less. Therefore, Equation 6 canbe changed as follows:

f min min Comparison of Equation 7 with Equation 1 shows that the effectof C can be neglected.

FIG. 18 shows an arrangement wherein one end of a variable capacitancediode 909 is high frequency-wise grounded and the other end thereof isconnected with a tuning circuit 910 and a capacitor 911 is coupled withthe other end of the tuning coil 910.

E is a power source from which a different voltage is applied to thevariable capacitance diode 909.

The operation of the arrangement shown in FIG. 18 Wlll now be described.A signal appearing at a terminal 908 is delivered to a series resonancecircuit formed by the variable capacitance diode 909, tuning coil 910and condenser 911 through the tuning coil 910, and the signal thus tunedis taken out from a terminal 912 of the series resonance circuit.

Thus, the following effect can be produced.

In the Iapanses television system, the center frequency of the lowestchannel is 93 mc., and that of the highest channel is 219 me. From this,the following result can be Since variable capacitance diodes of whichthe ratio of the maximum to the minimum capacitance is approximately maxhave recently been developed, it is possible to realize Equation 7. Thatis, in the conventional VHF tuners using variable capacitance diodes,the switching operation between the higher band and the lower band wasperformed through the use of a switch or other means. In accordance withthis embodiment of the present invention, however, the entire VHFtelevision channels can be selected without performing such switchingoperation.

In the American system, the lower band is in the range of 54 me. to 88mc., the center frequencies of the highest and lowest channels being 85mc. and 57 me. respectively,

and hence fmax 2 .2 frnin 2 Therefore, from Equation 7, it will be seenthat the ratio of the maximum to the minimum capacitance of variablecapacitance diodes in use may be about 2.2

( limax antu If the distributed capacitance C amounts to 4 pf. or more,the influence by the distributed capacitance is no longer negligible.Since the minimum value C of the variable capacitance diode is normallynearly 6 pf., the maximum value C is calculated from Thus, assuming thatC =4 pf., (C /C )=3.0. When a conventional variable capacitance diode of(C /C )=3.0 is more expensive of min and that other technical problemswill arise from the expanding of the range of voltage applied to thevariable capacitance diode to achieve IUBX 0min 3.0

then arrangement of FIG. 18 will become useful. In the case where anapplied voltage must be decreased to a low value, the rate of change ofthe junction capacitance of the variable capacitance diode with respectto voltage will become so high that cross-modulation and otherdisturbance due to the presence of non-linear elements will inevitablyoccur. In accordance with the present invention, the range of voltagerequired for the necessary capacitance variation range can be madenarrow as compared with that in the conventional circuits, therebyeliminating the disturbance stemming from the attainment of saidvariation range.

In the foregoing, description has been made of the method of receivingthe entire television broadcast signal band including the higher andlower bands and the method of applying a channel selection controlvoltage. Now, description will be made of a channel selectingarrangement wherein said methods are automatically carried out. FIG. 19shows an example of such arrangement, wherein the reference numeral 1001denotes a tuner including a high frequency tuned amplifier circuit 1002,a mixer circuit 1003 and a local oscillator circuit 1004. Variableselecting, tuning and oscillating elements of this tuner 1001 arecomposed of variable capacitance diodes. By changing a voltage appliedto these variable capacitance diodes to change the capacitance values ofthe latter, the tuning and oscillating conditions of the high frequencytuned amplifier circuit 1002 and the local oscillator circuit 1004incorporated in the tuner are so varied as to select a desiredtelevision broadcast channel.

In the tuner 1001, a frequency tuned in the high frequency tunedamplifier circuit 1001 and a frequency produced by the local oscillatorcircuit 1004 are supplied to the mixer circuit 1003 to be converted intoan intermediate frequency which is in turn supplied to an intermediatefrequency amplifier circuit 1005 having such a characteristic as shownin FIG. 21.

The reference numeral 1006 represents a detector circuit which isadapted to detect the intermediate frequency signal. The latter signalispartially supplied to a frequency discriminator circuit 1007 prior tobeing delivered to the detector circuit 1006. Thefrequency-discriminator circuit 1007 is so designed as to provide anoutput voltage corresponding to the intermediate frequency, as shown inFIG. 20. That is, if the intermediate frequency is deviated from areference point A, there is produced a DC output voltage correspondingto the deviation, which is in turn supplied to a trigger circuit 1009through a gatecircuit 1008.

The trigger circuit 1009 is designed so that it operates to produce apulse-like output voltage if the output voltage of the frequencydiscriminator circuit 1007 is deviated from the set reference point A byany small amount.

Such pulse-like output voltage is also produced by turning on a switch1010 of the trigger circuit 1009 whereby a sweep circuit 1011 iscontrolled.

Closing the switch 1010 causes the trigger circuit 1009 to produce thepulse-like output voltage by which the sweep circuit 1011 is operated.

This sweep circuit 1011 has its voltage successively varied with timeand the output of which is applied to the variable capacitance diodesserving as the variable tuning element and oscillation frequencychanging element included in the high frequency tuning circuit 1002 andlocal oscillator circuit 1004 constituting the tuner 1001. If each ofthe variable capacitance diodes is controlled by the output voltage ofthe sweep circuit 1011 so as to possess a capacitance value suitable toreceive certain television broadcast, such broadcast can be received,and the signal thus received is delivered to the intermediate frequencyamplifier 1005 thorugh the mixer 1003 and then to the frequencydiscriminator circuit 1007.

In case the intermediate frequency which has arrived at the frequencydiscriminator circuit 1007 is a normal one, then the output voltage ofthe discriminator has the value corresponding to the point A of FIG. 20,so that the output voltage applied to the trigger circuit 1009 becomeszero.

As a result, the trigger circuit 1009 is prevented from producing anyoutput voltage so that the output voltage of the sweep circuit 1011 maybe maintained at a constant value, thereby making it possible to receivea desired television broadcast signal.

Such conditions are illustrated in FIGS. 22A, B, C and D. FIG. 22A showsthe opening and closing conditions of the switch 1010. If the switch1010 is temporarily turned on, the trigger circuit 1009 operates torender the sweep circuit 1011 operative. FIG. 22C illustrates theresulting output waveform, and FIG. 22D shows the output voltagewaveform obtained from the trigger circuit 1009 of the sweep circuit1011. The output voltage of the sweep circuit 1011 is successivelyincreased in a stepped manner and it is returned to the original statewhen the entire channel or the lower "band is received.

Although the output voltage of the sweep circuit 1011 is kept constantduring reception, when the frequency of local oscillation is drifted dueto variations in the values of the variable capacitance diodes and othercomponents incorporated in the tuner 1001 and variations in the powersource voltage, a small output voltage is produced to auto-- maticallycontrol the drifted local oscillation to the normal frequency, and itdepends upon the deviation of the intermediate frequency arriving at thefrequency discriminator circuit 1007.

Since a television signal carrier wave consists of a video carrier waveand an audio carrier wave, the aforementioned arrangement will have sucha disadvantage that the automatic tuning circuit tends to be tuned tothe audio carrier wave even if it is desired to control the automatictuning circuit with the aid of the video carrier wave. Obviously, thetuning should be effected with respect to either one of these carrierwaves.

To this end, the synchronizing signals are separated by a synchronizingsignal separator circuit 1012 and rectified by a rectifier circuit 1013so as to be supplied to the gate circuit 1008 so that the gate circuit1008 may be opened to pass a signal from the discriminator 1007 whilereceiving an input signal from the rectifier circuit 1013. The signaldelivered from the freqeuncy discriminator circuit 1007 to the triggercircuit 1009 can be limited to the video signal component, therebypreventing any erroneous tuning operation from being caused by the audiocarrier wave.

Furthermore, a flip-flop circuit 1014 is driven by virtue of therepetition of the saw-tooth wave voltage produced by the sweep circuit1011.

For example, the flip-flop circuit 1014 may be driven in such a mannerthat the circuit produces a positive output or a negative output eachtime odd numbered sawtooth portions of the saw-tooth wave output areapplied thereto from the sweep circuit 1011.

A gate circuit 1015 is operated by the output of the flipflop circuit1014 to change the voltage of a power source 1016 which is applied tothe tuner 1001, thereby performing the switching operation between thehigher and lower bands of the VHF band. 1

By combining the sweep output with the output of a multi-vibrator (notshown), it is possible to develop this arrangement into a three-bandsystem including one UHF band and two VHF bands. Although, in theforegoing, description has been made of the case where the frequencydiscriminator circuit 1007 is used, use can equally be made of any othercircuit which is so designed as to produce an output voltagecorresponding to the deviation of the intermediate frequency.

As described above, in accordance with this invention, the intermediatefrequency carrier wave is frequency-discriminated, and the resultingoutput is supplied to the trigger circuit through the gate circuit whichis operated by the synchronizing signals. Then the sweep circuit iscontrolled by the trigger signal provided by the trigger circuit, andthe output voltage of the sweep circuit is applied to the variablecapacitance diodes of the tuner to effect automatic channel selection.In the conventional television receiver, such automatic selection wastechnically very difficult to achieve because of the fact that thetelevision carrier consists of two types of carrier waves, or a videocarrier wave and audio carrier wave. In accordance with this invention,however, such difficulties can effectively be removed by using a gatecircuit which is so designed as to be operated by synchronizing signals,

thus making it possible to achieve automatic television channelselection.

In addition, if the freqeuncy of local oscillation is drifted due tovariations in the values of the variable capacitance diodes and othercomponents incorporated in the tuner and variations in the power sourcevoltage, such drift is automatically compensated so that the localoscillation has the normal frequency by suitably adjusting the operatingpoint with respect to the discrimination of the intermediate frequencyand that of the trigger circuit.

What is claimed is:

1. A tuner comprising: a high frequency amplifier circuit having a tunedcircuit, the tuned circuit elements of which are constituted by variablecapacitance diodes; a local oscillator circuit having a resonantcircuit, the resonant circuit elements of which are constituted byvariable capacitance diodes; a mixer circuit for mixing the output ofsaid high frequency amplifier circuit with the output of said localoscillator circuit; and a control voltage source means for supplying acontrol voltage to each of said variable capacitance diodes to changethe tuned and resonant frequencies; each of said tuned circuit andresonant circuit including a first inductor coil, a second inductor coilcoupled with said first inductor coil to increase the total inductanceof the coils, a switching means connected in parallel with said secondinductor coil and an electric potential source of a single polarity;said switching means serving to apply a potential from said potentialsource of a single polarity to said second inductor coil to selectivelychange the effective inductance of said second inductor coil, wherebychange-over of the tuner is effected between a relatively higherfreqeuncy band and a relatively lower frequency band.

2. A tuner as set forth in claim 1, wherein said first and secondinductor coils are directly coupled with each other and said switchingmeans comprises another variable capacitance diode connected to theconnection point of said coils and to said electric potential source soas to be supplied with two different potentials of a single polaritythrough a switch.

3. A tuner as set forth in claim 1, wherein said first and secondinductor coils are coupled with each other through a magnetic coreconstituting a magnetic path between said coils, and said switchingmeans comprises a switch in parallel-with said second inductor coil toselectively make the latter inoperative.

4. A tuner as set forth in claim 1, further comprising a remote controlmeans comprising a band selection switch connected through lead wireswith said second inductor coils for effecting the change of theeffective inductance of each said second inductor coil and a variableresistor for the channel selection interlocked with said band selectionswitch.

5. A tuner comprising: a high frequency amplifier circuit having atleast one tuned circuit, the tuned circuit elements of which areconstituted by variable capacitance diodes; a local oscillator circuithaving a resonant circuit, the resonant circuit elements of which areconstituted by variable at least one capacitance diode; a mixer circuitfor mixing the output of said high frequency amplifier circuit with theoutput of said local oscillator circuit; a frequency discriminatorcircuit for monitoring the output of said high frequency amplifiercircuit; a gate circuit operable to conduct the output of said frequencydiscriminator circuit in response to a synchronizing signal; a triggercircuit driven by the output of said gate circuit; a sweep circuitcontrolled by the output of said trigger circuit and connected with saidhigh frequency amplifier circuit and said local oscillator circuit toapply as a control voltage the output voltage of the sweep circuit toand vary the capacitance of each of said variable capacitance diodes insaid high frequency amplifier circuit and in said local oscilaltorcircuit to change the tuned and resonant frequencies; and a flip-flopcircuit operative in response to blanking pulses from said sweepcircuit, the output of 17 18 said flip-flop circuit being fed to saidhigh frequency 3,130,264 4/1964 Dietz 1785.8 amplifier and to said localoscillator circuit, whereby the 3,264,566 -8/ 1966 Kaufman et al 325465change-over of the tuner is effected between a relatively 3,309,6133/1967 Bell 325-462X lower frequency band and a relatively higherfrequency 3,354,397 11/1967 Wittig 325-459 band and the tuner isautomatically tuned to a desired 3,390,228 6/1968 Bell 33416X channel. 5

R f ct d RICHARD MURRAY, Primary Examiner e erences 1 e B. V. SAFOUREK,A t t E UNITED STATES PATENTS an Xammer 2,601,384 6/1952 Goodrich, Jr.33416X 10 2,745,961 5/1956 Pan 325458X 325463, 464; 334-12, 15

3,010,015 11/1961 Pepperberg 33412X UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 3, 544, 903 Dated December I 1970Yoichi SAKAMOTO Inventor(s) It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

The inventor 5 name should read Yoighi SAKAMO IO not Yoighi.

In the priority claims, the following errors should be correct The 6thpriority should read:

January 27, 1967 4217562 not January 27, 1967 42111507;

Two Japanese applications are missing from the claim and shou] be addedas follows:

May 23, 1967 42/33222 and February 10, 1967 42/11507.

Signed and sealed this 26th day of October 1971 (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Acting Commissioner of PatentAttesting Officer

